Cast valve seat insert



April 17, 1956 H. F. PRAssE ETAL 2,742,356

CAST VALVE SEAT INSERT Filed Ooi. 7, 1954 Y vloosel in the engine.

Y f k2,142,356 CssrfvALvE' SEAT INSERT Herbert F. Prasse, Gates Mills,and Adna A. Armstrong,

Mentor, Ohio, assignorsto Thompson Products, Inc., Cleveland, Ohio, acorporation of Ohio t A Application October 7, 1954, Serial No, 460,8724 claims. (ci. '7s- 171) y The present invention relates. to valve `seatinserts of ,the type employed in internal combustion engines.

While the valve seat'insertisa relatively simple struc-V One oftheprirnary,l problems ofthe iselection `of a suitable metal or alloyfor use in valve seat insertsl arises from what is known as collapseresistance.

Itis known that :when metals or alloys are heated to very high'temperatures for extended periodsof time,'they nidStean-:S w Patent o i2,742,356' Patented Apr. 17, 1956 Inline'with the above, a good valveseat insert should also maintain its hot hardness properties, i. e., itshould retain a substantial amount of its hardness even at the elevatedtemperatures at which the engine is operating. This ability to maintainits hardness governs to a large extent the degree of Contact which canbeVmaintained between the valve face and the valve seat insert attheoperating temperatures of the engine. i

. y The characteristics of the valve seat insert also have aV pronouncedeffect upon the valve lash changes evident I during voperation of theengine. VThese changes accumu late inthe valve train due to wear and thepounding down of the valve seat insert during use. It is desirable thatthe valve seat insert have characteristics which minimize these changes,as it is undesirable to make frequent adjustments on the valve lashduring operation of the engine.l f

,willqcongeal or set in an expanded state and willnot Y contract totheir original dimensions when cooled.` Since engine. valve ,seatinserts are normally press-itted in recesses in engine cylinder heads orblocks, the valve seat inserts become heated in theoperation'of theengine and mayexpand to a point where further expansion is` restrictedby.thel cylinder metal itself. When this point is reached, continuedexpansion'due to increased temperatures .will cause the insert to bowinwardly away'from the restraining shoulder or wall of the engine head,or block. If the bowed inserts reach the setting temperatureand are then,cooled from .this temperature, the insert metal shrinks jaway from theinsert recess and the insert becomes The lbowed and set inserts areknown asV co1lapsed`inserts and the temperature at which suchyinsertstake apermanent set is known as the collapse temperature.A l fin the past, valve lseat inserts for-the most part have been producedbyexpensiveforging, machining, and heat treating procedures.v The `best ofthese prior known inserts had to be annealed, hardened, quenched,tempered, and drawn to a Rockwell hardness of about 35 on the C scale'.The micro-structure of thesev inserts generally exhibited anaggregatefof Vcarbideswitli some martensite oriented inan'interdendritic pattern andh/aving some of the carbides in the grainboundaries and scattered throughout `l y the matrix. This structure,however, did not provide adequate collapse 'resistance at temperaturesabove `about Another problem which manifests itself particularly/'inengines employing gasolines having a relatively high percentageofrtetraethyl lead is that of surfaceresistance.

A good insert must have a smooth face which resists deposit build up,corrosion, erosion, pitting, or excessive wear. Otherwise, anunsatisfactory seal will result between the valve seating face and thevalve seat insertring.

y'A lcharacteristic possessed by a good valve insert ring is that oflack of anity for the carbonaceous materials and lead deposits presentin the combustion chamber. These materials tend to become deposited onvalve seat insert rings and act as effective heat dams, thereby increasying the valve head'temperatures.

`.All of the above factors indicate that the problem of selecting asuitable alloy for `valveseat insert ringsis quite substantial. 1

In view of the foregoing, the need still remains in the art for a moresatisfactory valve seat insert ring, and the satisfaction of that needis the primary object of the present invention. j

vAnother object of the present invention is to provide an `improvedvalveseatinsert ring whichpis less expensive andmore convenient tomanufacture than the type of p valve seat `insert rings being presentlyemployed in many types of internal combustion engines.

. Other and further objects of this invention will be apparent to thoseskilled in the `art in the foregoing detail description of the annexedsheet of drawings which, by way of example only, illustrates a valveseat insert of s this invention.

On ythe drawings: f

Figure lisa plan view of the valve seat insert ring of the present`invention; s

- Figure 2 is a fragmentary view, with parts inl elevation, of the valveport area of an internal combustion engine, showing the valve seatinsert in its normal condition;

Figure 3 is a greatly enlarged fragmentary view of the valve port area,illustrating theinsert ring in its normal condition; l f

Figure 4 is a view similar to FigureA 3, but illustrating the ring inits collapsed condition;

Figure 5 is a graphic reproduction of a micro-structure of the alloyconstituting the insert, at a magnilcation of about 500 times.

Asrshown on the drawings:

From Figures l to 4, it will be seen that the engine valve port assembly10 Vmay include an engine block or cylinder head 11 normally composed ofcast iron, and a cast valve seat insert 12 press fitted intoa. recess 13of the engine,block or cylinder head 11. A bore 14 concentric with therecess 13 is provided to receive avalve stem l guide 16 in the usualmanner. A'valve 17 is shown in 'seatedrelation in the valve seat .insertring 12 (Fig. 2),

'the valve 17 having a stem 17a slidably received withinV the valve stemguide 176. j g

The valve seat insert-ring 12 may consist of a ring having acylindricalrouter peripheral Wall 12a, a llat bot- V tom 12b, a ilat top12e and a tapered seating face 12d convergingfrom the ilat top 12e to acylindrical inner peripheralvwall 12e.

The peripheral wall 12a is in snug fitting relation with In normaloperation, the valve seat insert ring 12 mainstantially the same degreeas the metal in which-the recess 13 is formed. However, when the valveseat insert 1 2 isl heated to'a point where it can expand no further dueto the restraining effect of the walls of the` recess, it may becomeVbowed as illustrated in Figure 4. This bowing may create a gapillustrated at 19 in an exaggerated form in Figure 4Q If the insert 12is Afcollapsed in the condition shown in Figure 4, then the gap 19 willremain void underk lower operating temperatures. `As a result, theinsert 12 will remain loose in the recess 13.

We have now found that the collapse temperature of valve seat insertscan be increased, and other desirable properties of the insertsenhancedby employing a cast valve seat insert having the followingcomposition:

' y l i -Percent Carbon l Y 2.25 to 2.75 Nickel 37 to 43 Chromium Y 18vto 22 Cobalt l0 to l4 Tungsten, molybdenum or mixtures thereof 5 to 7Iron- Substantially the balance A particularly preferred compositionforvalve insert rings has the following analysis:

1 Percent n lron Substantially the balance For the purposes of thisinvention, molybdenum and tungsten are substantially intt-zrchangeable.AWhere the hardness of the insert is of prime importance, tungsten Carbon2.5 Nickel` 40. Chromium 20 `Cobalt. 12 Tungsten 6 Y The insert isheated rst torabout 300 F. for several hundred cycles of operation. Itis then cooled and cheeked for looseness. The temperature is thenincreased in increments and the heating is repeated for several hundredcycles. The procedure is continued until the insert under testloosensrin the cast iron cup. The nal temperature is then recorded asthe loosening temperature or collapse temperature. The collapseresistance of four insert rings having compositions Within the rangesgiven The resistance of the insert rings to corrosion by lead oxide wasdetermined in 'a standard test in which the samples are packed in leadoxide and maintained at a temperature of 1675 F. for one hour irranYoxidizing atmosphere The decrease in weight after thetest, expressed ingrams per square decimeter, is taken as the lead oxide corrosion loss.When tested under the conditions given, valve seat insert rings havingcompositions within the ranges indicated above showed an average loss ofonly 3.5 grams per square decimeter. In contrast, samplesof variouscommercial valve seat inserts of compositions different from that of thepresent inventions alone may be employed as in the above preferred com-.n

position. Where toughness is the objective, molybdenum alone VYmay beused.V If desired, a mixture of the two metals may be used to secure thebenefit of each, as in the following composition:

y p Percent Carbon Y 2.5 Nickel 40 Chromium 20 Cobalt 1 2 Tungsten 3Molybdenum Y 3 Y lron Substantially the balance and cast in suitablemolds for `producing the insert ring vl2. Thec'arsting process employedVmay includejconven` tional sand casting, shell molding, investmentcasting, 0r other casting techniques capable of producing smooth,accurate castings free from cracks, blow holes, shrinks and the like.

Thecast insert rings need no special heatV treatment, 'i5 making themconsiderably. easier and less expensive toY manufacture than commonlyused insert rings which frequently require hardening and drawing stepsincidnt to their manufacture. Y

Y The micro-,structure `of ythe finished valve seat insert rings isillustrated in Figure 5 of the drawings. It will be observed that thestructure'may include dendrites 21 surrounded by a solid solution 22consisting of an eutectic matrix. l

A convenient collapse test for the rings consists in inserting the ringunder Vtest in cast iron cup receiving a lhigh frequency induction coilin the hollow interior of the ring.- The cast iron cup isrsurroundedv bya water ring. The insert lis then'intermittently heated by the inductioncoil and cooled by a water spray on theicast cup.

lost up toseveral hundred grams per square decimeter under the identicaltest conditions. v 'ln addition to the' foregoing, valve seatl insertsmade in accordance -with the present invention did not accumulate asignicant amount of combustion chamber deposits' on their' faces andevidencedno measurable loss .in hardness at the operating temperature ofthe engine. This, again, was in marked contrast to several commercialvalve seat inserts which had a substantial affinity for the combustionchamber deposits and lost a substantial amount iof their strength at theoperating temperature of the engine. i. i

A very significant advantage of the present invention arises from thevalve lash properties observed when valve seatA inserts of the presentinvention are employed in operating engines. In onesuch test, a heavyduty truck engine was provided withseveralvalve seat insert ringsproduced according to the present invention in several of its cylinders.The accumulated lash change. in the cylinders after 400 hours Vofoperation was Van increase of 0.004. inch. in other cylinders, highnickel alloy in; sert rings containing 58.7% nickel, .2.6% chromium,about 4% iron, and about 2.0% carbon were employed. The accumulatedvalve lash change for these inserts, in the sametest, was in excessvof0.010 inch.

From the foregoing, it will beaPPIeciated that the valve seat inserts ofthe present invention have exceptional r esistance to collapse,resistance to lash loss, and excellent corrosion resistance.The'additional properties of. good hot strength and resistance todeposits make the alloys of the present invention considerably moresatisfactory for the intended use than heretofore known more experisiveinserts. j

' While thealloy of the present invention has properties making itparticularly suitable in the' manufacture of `valveseat` inserts, itwill be appreciated that the alloy willhave more general applicability,for articles requiring wear and corrosion resistance properties. l

` It will be understood that modifications and variations maybeetectedwithout departing from the scope and novel concepts of the presentinvnntiom 'Y Y n i We claim as our invention: i

t l. A cast valve seat insert comprising a ring having the p followingcomposition:

2. A cast valve seat insert comprising airing having the followingcomposition:

Percent Carbon 2.5 Nickel 40 Chromium 20 'Cobalt 12 Tungsten 6y IronSubstantially the balance 3. The method of making Va valve seat inserthaving enhanced wear resisting and corrosion resisting properties whichcomprises forming a molten mixture of the following composition:

Percent Carbon 2.25 to 2.75 Nickel 37 to 43 ,Chromium 18 to 22 "Cobalt1o to 14 Metal selected from the group consisting of tungsten,molybdenum, and mixtures thereof 5 to 7 Iron Substantially the balanceand casting said mixture into the shape of a ring.

4. A method of making a valve seat insert having enhanced wear resistingand corrosion resisting properties which comprises forming a moltenmixture of the following composition:

t Percent Carbon 2.5

Nickel 40 Chromium 20 Cobalt 12 Tungsten 6 Iron Substantially Ythebalance and casting lsaid mixture into the shape of a ring.

References Cited in the iile of this patent Y UNITED STATES PATENTS Y Y2,214,810 Chesterfield Sept. 17, 194() 2,296,460 McDonald Sept. 22, 1942FOREIGN PATENTS 637,786 Great Britain May 24, 1950

1. A CAST VALVE SEAT INSERT COMPRISING A RING HAVING THE FOLLOWINGCOMPOSITION: PERCENT CARBON --------------2.25 TO 2.75 NICKEL--------------- 37 TO 40 CHROMIUM ----------------- 18 TO 22 COBALT------------------- 10 TO 14 METAL SELECTED FROM THE GROUP CONSISTING OFIRON ------------ SUBSTANTIALLY THE BALANCE